Comments

The legacy plane->fb pointer is refcounted by calling
drm_atomic_clean_old_fb().
In practice this isn't a real problem because:
- The caller in the i915 gpu reset code restores the original state
again, which means the plane->fb pointer won't change, hence can't
leak.
- Drivers using drm_atomic_helper_shutdown call the fbdev cleanup
first, and that usually cleans up the fb through
drm_remove_framebuffer, which does this correctly.
- Without fbdev the only framebuffers are from userspace, and those
get cleaned up (again using drm_remove_framebuffer) befor the driver
can even be unloaded.
But in i915 I've switched the cleanup sequence around so that the
_shutdown() calls happens after the drm_remove_framebuffer(), which is
how I discovered this issue.
v2: My analysis why the current code was ok for gpu reset and
suspend/resume was correct, but then I totally failed to realize that
we better keep this symmetric. Thanksfully CI noticed that for
balance, a refcounting bug must exist at 2 places if previously there
was no issue ...
v3: Don't be lazy and compute the plane_mask in
commit_duplicated_state properly too, instead of just using ~0U.
Cc: martin.peres@free.fr
Cc: chris@chris-wilson.co.uk
Acked-by: Dave Airlie <airlied@gmail.com> (v1)Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
drivers/gpu/drm/drm_atomic_helper.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)